Fuel cells are electrochemical devices that can convert suitable hydrogen or hydrocarbon fuels directly into electrical power. As such, fuel cells have promise as a way to obtain electricity from clean fuels. Fuel cells have been proposed as power sources for devices as diverse as automobiles, personal computers and flashlights.
There are a wide range of known fuel cell constructions. In a typical fuel cell system, multiple unit cells are associated together to make a fuel cell stack. Manifolds are provided to carry fuel and oxidant to anode and cathode regions of the fuel cell. Mechanisms for distributing these reactants and collecting the resulting reaction products (electrical current, water, heat) are also provided. In a fuel cell, the fuel is physically isolated from the oxidant. Sealing of the structure to prevent mixing of the reactants is always required.
Most fuel cell systems have the form of a rigid block of adjacent fuel cells made up of an alternating structure of rigid plates. The plates permit separate flows of reactants to thin unit fuel cells to produce electricity. Seals between the plates prevent leakage.
A problem with the designs of some fuel cell systems is that they are made up of large numbers of separate parts such as membrane electrode assemblies, current collectors, seals, and the like. This makes such fuel cell systems time-consuming and expensive to make. Fuel cell systems that have many separate cooperating parts can also be prone to failure due to leaks, electrical short circuits, electrical open circuits or the like. Another problem with some existing fuel cell designs is that the designs cannot be easily adapted to permit the fuel cell system to be shaped to fit in an available space.
For large stationary devices, the volume requirements of conventional fuel cell stacks is relatively inconsequential. However, in portable applications, space is at a premium. In order to maximize power to a portable device, the active area of fuel cells provided to power the device must be large. In order to maximize operational lifetime, the volume available for fuel storage must be maximized. Current portable fuel-cell-powered devices are designed around the space required by the fuel cells and fuel storage just like their battery-powered counterparts are designed around the space required by batteries. This has typically resulted in undesirably bulky devices.
There is a need for fuel cell systems and other electrochemical cells that are reliable and cost effective and provide design flexibility. There is a particular need for fuel cell systems that are useful for powering portable electronic devices.